Forms of Energy Mechanical energy is the energy possessed

by an object due to its motion or its position.

Radiant energy includes light, microwaves, radio waves, x-rays, and other forms of electromagnetic waves.

Nuclear energy is released when heavy atoms in matter are split up or light atoms are put together.

The electrical energy we use is derived from other sources of energy.

Kinetic Energy Energy of motion is called kinetic energy.

The kinetic energy of a moving object depends on two things: mass and speed.

Kinetic energy is proportional to mass.

Kinetic Energy Mathematically, kinetic energy increases as

the square of speed.

If the speed of an object doubles, its kinetic energy increases four times. (mass is constant)

Kinetic Energy

KE = 1 mv2

2

Speed (m/sec)

Mass (kg)

Kinetic Energy (joules)

Kinetic Energy

Kinetic energy becomes important in calculating braking distance.

Calculate Kinetic Energy A car with a mass of

1,300 kg is going straight ahead at a speed of 30 m/sec (67 mph).

Calculate:

a) The kinetic energy of the car.

Examples

Determine the kinetic energy of 625kg roller coaster car that is moving with a speed of 18.3 m/s.

Problem

Miss Diwater, the former platform diver for the Ringling Brother’s Circus, had a kinetic energy of 12,000. J just prior to hitting the bucket of water. If Missy’s mass is 40.kg, then what is her speed?

YOU TRY!

Pg. 174 # 1-5

Work-Kinetic Energy Theorem

Wnet = ΔKEOr

Wnet = 1/2mVf2 – 1/2mVi

2

Net work = change in kinetic energy

Example

On a frozen pond, a person kicks a 10.0 kg sled, giving it an initial speed of 2.2m/s. How far does the sled move coming to a complete stop if the coefficient of kinetic friction between the sled and the ice is 0.10?

YOU TRY

Pg. 176 #1+2